Recurring Addon Extension: Adding placeholder for custom recurring donations

/* 

 * This will work only for Charitable Recurring Donations 1.4.0.4+

 * This accepts the HTML of the text box and with a little fancy replacing, allow you to add attributes.

 */ 

add_filter( 'charitable_recurring_custom_amount_input', 'test_charitable_recurring_custom_amount_input', 10, 4 );

function test_charitable_recurring_custom_amount_input( $html_input_text, $campaign, $amount, $form_id ) {

	$html_input_text = str_replace( 'type=', 'placeholder="Enter amount"', $html_input_text );

	return $html_input_text;

}